Summary Adrenergic receptors (ARs) are a family of prototypical GPCRs linked to neuronal disorders, metabolic syndrome, and cardiovascular diseases. In the CNS, norepinephrine (NE) regulates attention and alertness. The ?2AR is emerging as the prevalent postsynaptic NE effector at glutmatergic synapses, where it interacts with AMPAR, NMDAR and L-type Ca2+ channel Cav1.2 to modulate neuronal excitability, synaptic plasticity, and memory and learning. It is clinically relevant to understand NE-linked mental diseases such as depression, attention deficit hyperactivity disorder (ADHD), anxiety disorders (e.g., posttraumatic stress disorder, PTSD) and Alzheimer's disease. While ?-blockers are used to treat a variety of peripheral diseases including heart failure, hypertension, glaucoma, asthma, and COPD, their clinical utility is hampered by the side effects including anxiety and depression. Recent explosion of crystallography study of ligand-GPCR interactions, there is still limited understanding on how a specific ligand leads to pleotropic cellular responses (including sides effects) of a GPCR. In this study, we hypothesize that a distinct subpopulation of PKA-phosphorylated ?2ARs control LTCC activation in hippocampal neurons, which can be selectively activated by a set of biased ligands. We will test our hypothesis with following specific aims: Aim 1 is to test the hypothesis that ?2AR can exist in distinct functional subpopulations in a single mammalian cell. We will use biochemical isolation/fractionation and super-resolution imaging to characterize distinct subcellular distribution of PKA-p?2AR and GRK-p?2AR. Aim 2 is to test the hypothesis that PKA-p?2AR transduce biased signal through selectively modulation of ion channel activity at the plasma membrane (PM). Aim 3 is to test the hypothesis that sympathomimetic ?-blockers act as biased ligands that selectively activate PKA-phosphorylated subpopulation of ?2AR to activate ion channel at the PM. If successful, these aims will reveal a platform to understand the biased signaling induced by two distinct subpopulations of ?2AR, and offering a new avenues for designing more efficacious ?-AR drugs with fewer side effects in clinical applications.